Batteries stored for long periods of time can lose capacity from internal self-discharging as a result of irreversible side reactions that consume charge carriers without producing current. Because no cell is a perfect insulator, cells in a battery can noticeably self-discharge to some degree while the battery is idle or in a quiescent state. A quiescent state can occur for example when the battery is not in use and not being charged or balanced. A certain amount of self-discharge in a cell can be compensated for during cell balancing and charging by discharging the other cells to bring them to the same level of state of charge as the self-discharged cell. However, a particular cell's self-discharge rate may exceed what can be compensated for during the balancing and charging process. In this case, it may be necessary to replace the self-discharging cell or to recommend a remedy to address the issue before it causes battery failure. Accordingly, a technique for estimating and monitoring a self-discharge rate would be advantageous for use as a measure of battery health.